Conventional sports rackets have strings which are effectively anchored as they pass through string holes, formed through the head frame of the racket. This effectively divides the string into individual string chords which span the head frame. The effective isolation of each string chord causes localized high dynamic string tension in each chord as it contacts a ball. Static and dynamic string tension are known to affect various performance factors of a sports racket, including power and control.
Devices for transmitting or equalizing string tension between adjacent sports racket string chords were shown and described in U.S. Pat. Nos. 4,930,782 and 4,591,165. The rocker devices described in those patents served to increase the effective length of string chords and to thereby reduce the peak tension in the racket strings while hitting a ball. This resulted in increased power, lower vibration and stress in the racket frame, and more balanced restoring forces. These constructions also provided a more uniform rebound response for impacts occurring over the various areas of the string hitting surface.
To achieve these results, individual string rockers were placed between adjacent string holes in the racket head frame. Each rocker was comprised of an elongated member having a length approximately equal to the distance between two adjacent string holes. The upper surface of each rocker had a groove for receiving a string.
During assembly, a string was threaded outward through a first string hole, over the rocker, and then inward through a second, adjacent string hole. The string thus was trained over the rocker. When tensioned, the adjacent string chords applied inward force to the rocker which retained the rocker. The string forces were transferred through the rocker and against the racket frame. The curved bottom surface of the rocker caused rocking to occur when the string chords experienced different tensile forces. This allowed tension from one string chord to be transmitted to the adjacent string chord. The string holes were large enough to allow unimpeded passage of individual strings, so as not to anchor strings as they passed through the string holes.
The rocker devices described above provided an important and dramatic performance improvement over previously known sports rackets. However, assembly and use of these rackets was not without problems. For instance, it was difficult to retain individual rockers in place during stringing. A broken string could result in some or all of the rockers being lost from the racket, and possibly scattered over a playing court. Restringing involved the same problems as original assembly, while also requiring the need for the user or repairer to stock spare rockers to replace those lost after a string break.
The invention described below provides an effective solution to the noted deficiencies in previous rocker-equipped rackets. The invention also provides a number of other advantages and features which are explained or can be appreciated from the description given herein.